Method for transmitting power and data in a bus system provided for occupant protection devices

ABSTRACT

Information data and energy are transmitted from a central control to control modules through a bus system in an occupant protection system including occupant protection devices such as airbags. In order to avoid overloading the protection system due to an immediate recharging of an energy storage member after that member triggers an occupant protection device, such recharging is suppressed or interrupted, preferably until a reset command signal is received by the respective control module from the central control.

FIELD OF THE INVENTION

The invention relates to a method for transmitting power and data in abus system for occupant protection devices in vehicles. The inventionalso relates to a control module for performing the method.

BACKGROUND INFORMATION

Methods and devices for performing such methods are known from GermanPatent Publications DE 44 41 184, DE 196 43 013, and DE 197 51 910. Therespective goal is to safeguard the safety relevant peripheral controlmodules against short duration disturbances, for example interruptionsor overloads of the d.c. voltage from a bus system required for thepower supply. Furthermore, in the conventional methods, digital data aretransmitted over the same conductor section, with the power supply, byvoltage modulation of the d.c. voltage. U.S. Pat. No. 4,736,367 and aMotorola Semiconductor Application Note AN475/D by Burri/Renard: “SingleWire MI Bus controlling stepper motors”, 1993, also disclose d.c.voltage modulated data transmission.

The special problem of current loading of the bus system duringsimultaneous transmission of power and data has been describedparticularly in German Patent Publications DE 196 43 013 and DE 197 51910. Thus, there is the risk that it will be impossible to process thedata.

For example, in bus systems in motor vehicles, direct current or d.c.voltage is usually used for the power supply, onto which the data can bemodulated. Due to an excessively high current consumption or otherfactors that act upon the d.c. voltage, the data modulated onto the d.c.voltage can become unrecognizable.

The data transmission, particularly for safety relevant bus systems forpower and data transmission with several control modules arranged withinthe bus system, which modules are also to be triggered sequentially,must not be jeopardized, for example, by an ignition of initial occupantprotection devices. For this purpose methods for providing extra energyare described in addition to the energy storage (autarchic capacitors)provided in the peripheral control modules. This extra energy may, forexample, be needed for igniting the occupant protection devices. Thesemethods provide the extra energy in a way that does not load the bussystem. Thus, the energy storage devices are preferably charged in thetransmission pauses or are charged with very low current consumptionfrom the bus system.

A problem with the above methods is seen in that the energy storagedevices are severely discharged when an occupant protection device istriggered and consequently a recharging from the bus system startsdirectly thereafter. Even with current limit circuits that are provided,this recharging can result in a high load on the data transmissionsystem when several occupant protection devices are triggeredsimultaneously and therefore their energy storage devices must berecharged. It is then possible that control modules of occupantprotection systems that are triggered later cannot be timely triggeredagain at the right time, or possibly interrogation routines to be madecannot be carried out.

Heretofore, only the resistance check in a pyrotechnical igniter of anoccupant protection device is known as a method for verifying anexecuted triggering subsequent to a trigger command. An intact, not yettriggered pyrotechnical igniter has a low resistance. When thepyrotechnical igniter triggers, the ignition wire is either interruptedor in individual cases, can also be short-circuited. A check cantherefore be faulty. In addition, the verification is not applicable forother ignition concepts, for example with cold gas generators.

SUMMARY OF THE INVENTION

For the above reasons, it is an object of the invention to provide amethod of the above described type wherein an additional load on the bussystem subsequent to triggering of individual occupant protectiondevices can effectively be avoided. In addition, a method for verifyingan executed triggering subsequent to a trigger command is shown. Thismethod is based on one of the preceding methods, is very simple and canbe reliably implemented. Furthermore, a control module for implementingthe method is indicated.

According to the invention energy and data are transmitted through a bussystem in an occupant protection system including a central processingunit (7), triggerable occupant protection devices (1.1) communicativelyconnected through control modules (6) and through said bus system (5) tosaid central processing unit (7), wherein the following steps areperformed:

(a) transmitting data and energy between said central processing unitand said control modules through said bus system,

(b) providing a respective energy storage device for each respectivecontrol module of said control modules,

(c) charging said respective energy storage device through said bussystem for a limited time to assure proper operation of said respectivecontrol module and of an occupant protection device connected to saidrespective control module,

(d) normally maintaining a charged state of said respective energystorage device, and

(e) interrupting said charging and maintaining of the energy storagedevice of the respective control module in response to an executedtriggering of a respective occupant protection device.

An essential feature of the invention is that the charging or rechargingof the energy storage device of the already triggered occupantprotection devices and/or of the corresponding control modules isinterrupted. In this way, the bus system can continue to transmit thedigital data undisturbed and the control modules of the occupantprotection devices that have not yet been triggered can receive theirdata. This interruption or suppression can be realized in a particularlysafe way and free of loss by high-resistance separation. It isparticularly preferable to interrupt the recharging at least until areset command. The reset command resets the peripheral control modulesagain and then begins with the recharging of their energy storagedevices. The energy available in the energy storage device of anoccupant protection device, after the device has been triggered, can beused advantageously for checking and recognizing a successfultriggering. If, for example because of a break in the conductor to theigniter of the occupant protection device, the device cannot betriggered, then the energy does not flow from the energy store. Thissituation can be recognized by a comparison with a rated value and canbe displayed or other measures can be taken.

According to the invention there is also provided a control module foran occupant protection system including a central processing unit,triggerable occupant protection devices communicatively connectedthrough control modules and through said bus system to said centralprocessing unit, said control module comprising a switch normallyconnecting an energy storage device to said bus system for charging saidenergy storage device through said bus system, a control signalgenerator operatively connected to said bus system for receiving atrigger signal, said control signal generator having a control outputconnected to said switch for interrupting said switch after said triggersignal has been received by said control signal generator.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be clearly understood, it will now bedescribed in connection with example embodiments, with reference to theaccompanying drawings, wherein:

FIG. 1 shows a block diagram of a data transmission system according tothe invention; and

FIG. 2 shows a block diagram of details of an occupant protection devicewith a control module and energy storage devices according to theinvention.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BESTMODE OF THE INVENTION

FIG. 1 shows a block diagram of a bus system for transmitting power anddata. This bus system comprises a central processing unit 7 which isconnected by the bus system 5 to a plurality of peripheral controlmodules 6. Also shown schematically in FIG. 1, by way of example, is theselected voltage modulated power and data transmission. The d.c. voltageU(t) generated by the central processing unit 7 provides the powersupply. The digital data to be transmitted are modulated onto the d.c.voltage by way of voltage modulation.

For this purpose the d.c. voltage amplitude that is as such constant, isrespectively varied. The types of modulation and encoding used for thispurpose, for example pulse width modulation, are known in the prior art.The central processing unit 7 is usually constructed as amicrocontroller circuit that receives safety relevant signals fromsensors such as acceleration sensors, processes these signals, anddrives the occupant safety devices accordingly through the bus system 5.An occupant protection device 1.1 is allocated to each of the controlmodules 6 which drive and, if necessary, trigger the respective devices.Thus, the control modules 6 receive and process the data transmittedfrom the central processing unit 7, implement internal processes, forexample control or programming steps, and trigger, if necessary, theoccupant protection device, for example an airbag. In addition, thecontrol modules 6 can also send data back to the central processing unit7.

By way of example, the essential components for performing the methodfor a peripheral control module 6.x are shown in greater detail. Heretheir functions shall be explained only within the context of themethod. Thus, each peripheral control module 6 has an energy storagedevice 1.4 that can be constructed as an autarchic and/or ignitingcapacitor and/or accumulator as a buffer or an intermediate energystore. It is also conceivable that several energy storage devices areprovided in one control module. It makes sense therefore, to reduce theload on the bus system 5, to initially interrupt the recharging of allthe energy storage devices 1.4 in the respective control module 6.xsubsequent to a triggering of the corresponding occupant protectiondevice 1.1.

This interruption of the recharging is done, for example by acontrollable switching means 1.8 which, in the microelectronicrealization, is usually constructed of a transistor arrangement and, aswill be explained later with reference to FIG. 2, can also beconstructed as a controllable charging unit. The switching means 1.8 isdriven by a control unit 10 by a signal s3. The control unit 10 ispreferably a microcontroller and satisfies all control tasks within thecontrol module 6.x. The control unit 10 receives and processes the datatransmitted on the bus system 5, allocates the data that are relevant orintended for the respective control module (6.x) and triggers thecorresponding functions in the control module 6.x.

In order to carry out the method, the control unit 10 must recognize atleast the trigger command to the control module 6.x. Subsequent totriggering the occupant protection device 1.1, the control unit 10interrupts the recharging of the energy store 1.4 by means of the signals3 to the controllable switching means 1.8. Preferably, the control unit10 can also receive and/or derive a reset command from the centralprocessing unit 7 through the bus system 5 and will subsequentlyterminate the interruption of the recharging, that is, close again theswitching means 1.8 through the signal s3. For this purpose, the controlunit 10 is connected in parallel to the switching means 1.8 and with thebus system 5.

In addition to a specified code word, a voltage reset is particularlyadvantageous as a reset command, that is, a drop in the d.c. voltagelevel by a defined measure, for example, a drop approaching 0 volts fora certain time. This is very simple to realize and is very easy torecognize. Also, a voltage reset can trigger a plurality of otherprocesses that go beyond the method, but are nevertheless processes thatlogically belong together temporarily, for example clearing memories,resetting the microcontroller of the control module, etc.

In addition to the parallel connection of the control module 6 to thebus systems 5 shown in FIG. 1, the method is also suitable for serialbus systems.

FIG. 2 shows a further developed embodiment of the device shown in FIG.1 and an occupant protection device similar to the type disclosed inGerman Patent Publication 197 51 910 and its control module with anignition current circuit comprising an ignition energy store 2, aswitching means 3, and the electric igniter 1.

The ignition current I4 from the ignition energy storage 2 to theigniter 1 is connected by the switching means 3 in response to a firstsignal s1 from the control unit 10. When the switch 3 is closed theignition current I4 triggers the igniter 1. An intermediate storagedevice 4, constructed as an accumulator, is connected to a point betweenthe bus system 5 and the ignition energy storage 2. Additional controlmodules 6 are connected to the bus system 5, for example for otheroccupant protection devices, crash sensors, or other motor vehicleelectronic control modules. A central processing unit 7 is alsoconnected to an end of the bus system 5. The central processing unit 7controls the data modulated voltage supply into the bus system 5. Theintermediate storage device 4 is charged by means of a charger unit 8that limits the charging current I1 to a predetermined maximum value andthus, in addition, electrically decouples the intermediate storagedevice 4 from the bus system 5. A converter 9 is arranged between theintermediate storage device 4 and the ignition energy storage device 2.The converter 9 is drivable by means of a second signal s2 from thecontrol unit 10 depending on the operating state and the triggercommand. The control unit 10 gathers the data modulated onto the voltageof the bus system 5 and recognizes from the data the operating state aswell as, if applicable, a trigger command. The control unit 10 generatesthe respective signal s1 for driving the switch 3, the signal s2 for theconverter 9, and the signal s3 for the charging unit 8.

The switching means 1.8 shown in FIG. 1 are constructed as a charger 8in FIG. 2. The charger 8, is driven by the control unit 10 through thesignal s3. Thus, after triggering the occupant protection device 1.1 bymeans of the igniter 1 through the signal s1 from the control unit 10,the charger 8 is blocked by the signal s3, whereby recharging istemporarily interrupted. When the control unit 10 recognizes a resetsignal from the bus system 5, then the charger 8 is again activated bythe signal s3.

A method for checking whether an occupant protection system hastriggered in response to a trigger command offers itself as a furtherexample embodiment for both previously described example embodiments.With this method a short time after suppressing the recharging of theenergy storage device, the content of the energy storage device iscompared with a rated value and, if the energy content is greater or thesame as the rated value, it is recognized that triggering did not takeplace. A corresponding control device detects, for example, the voltageof the energy storage device 4, 1.4 and reports this detection to thecontrol unit 10, which then sends a corresponding signal through the bussystem 5 to the central processing unit 7.

Although the invention has been described with reference to specificexample embodiments, it will be appreciated that it is intended to coverall modifications and equivalents within the scope of the appendedclaims. It should also be understood that the present disclosureincludes all possible combinations of any individual features recited inany of the appended claims.

What is claimed is:
 1. A method for transmitting energy and data througha bus system (5) in an occupant protection system including a centralprocessing unit (7), triggerable occupant protection devices (1.1)communicatively connected through control modules (6) and through saidbus system (5) to said central processing unit (7), said methodcomprising the following steps: (a) transmitting data and energy betweensaid central processing unit (7) and said control modules (6) throughsaid bus system (5), (b) providing a respective energy storage device(1.4; 2) for each respective control module (6) of said control modules,(c) charging said respective energy storage device through said bussystem (5) for a limited time to assure proper operation of saidrespective control module and of an occupant protection device connectedto said respective control module, (d) normally maintaining a chargedstate of said respective energy storage device, and (e) interruptingsaid charging and maintaining of the energy storage device of therespective control module in response to an executed triggering of arespective occupant protection device.
 2. The method of claim 1, furthercomprising performing said step of interrupting by switching off saidrespective charging device from said bus system.
 3. The method of claim1, further comprising continuing said interrupting until a reset commandsignal is applied to the respective control module, the occupantprotection device of which was triggered.
 4. The method of claim 1,further comprising verifying whether or not said triggering of saidoccupant protection device has taken place, by comparing, after apredetermined time following said interrupting of said charging, anenergy content of said respective energy storage device with a ratedenergy value, and by recognizing that no triggering took place if saidenergy content is larger or equal to said rated energy value, andrecognizing that triggering took place if said energy content is smallerthan said rated energy value.
 5. A control module for an occupantprotection system including a central processing unit (7), triggerableoccupant protection devices (1.1) communicatively connected throughcontrol modules (6) and through a bus system (5) to said centralprocessing unit (7), said control module comprising a switch (1.8)normally connecting an energy storage device (1.4; 2) to said bus system(5) for charging said energy storage device through said bus system, acontrol signal generator (10) operatively connected to said bus systemfor receiving a trigger signal, said control signal generator (10)having a control output (S3) connected to said switch for interruptingsaid switch (1.8) after said trigger signal has been received by saidcontrol signal generator.
 6. A control module for an occupant protectionsystem including a central processing unit (7), triggerable occupantprotection devices (1.1) communicatively connected through controlmodules (6) and through a bus system (5) to said central processing unit(7), said control module (6) comprising an energy storage device, acontrol signal generator (10) operatively connected to said bus systemfor receiving a trigger signal, said control module further comprising acharger (8) for charging said energy storage device and a control output(S3) connected to said charger for switching off said charger (8) aftersaid trigger signal has been received by said control signal generator.